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Title: DEVELOPMENT OF BORIDIZED PASSIVATION LAYER FOR USE IN PEM FUEL CELLS BIPOLAR PLATES

Abstract

This paper outlines the development of a new low-cost materials concept for polymer electrolyte membrane fuel cells (PEMFCs). Employing the roll bonding process to prepare a nickel clad steel laminate, the thin outer nickel layer is then passivated using a powder pack boridization technique. Results from energy dispersive X-ray (EDX) and X-ray diffraction (XRD) analyses and from scanning electron microscopy (SEM) indicated that a relatively homogeneous Ni3B layer grows on the exposed surfaces of the nickel and that the thickness of this layer can be readily controlled through the time and temperature over which boridization takes place. At high boridization temperatures, ≥ 700ºC, and long periods of time, a Ni2B overlayer forms on top of the Ni3B. Preliminary exposure testing conducted at 80ºC for 300hrs in 1M H2SO4 containing 2ppm HF demonstrates a significant increase in the corrosion resistance that is attributable to the boridization treatment.

Authors:
; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
948423
Report Number(s):
PNNL-SA-48375
HI0300000; TRN: US200906%%340
DOE Contract Number:
AC05-76RL01830
Resource Type:
Conference
Resource Relation:
Conference: Advanced Ceramic Coatings and Interfaces: Ceramic Engineering and Science Proceedings, 295-304
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 30 DIRECT ENERGY CONVERSION; BONDING; CERAMICS; COATINGS; CORROSION RESISTANCE; ELECTROLYTES; FUEL CELLS; MEMBRANES; NICKEL; PASSIVATION; PLATES; POLYMERS; SCANNING ELECTRON MICROSCOPY; STEELS; TESTING; THICKNESS; X-RAY DIFFRACTION; bipolar plate; PEMFC

Citation Formats

Weil, K. Scott, Kim, Jin Yong, Xia, Guanguang, Coleman, J. E., and Yang, Zhenguo. DEVELOPMENT OF BORIDIZED PASSIVATION LAYER FOR USE IN PEM FUEL CELLS BIPOLAR PLATES. United States: N. p., 2006. Web. doi:10.1002/9780470291320.ch28.
Weil, K. Scott, Kim, Jin Yong, Xia, Guanguang, Coleman, J. E., & Yang, Zhenguo. DEVELOPMENT OF BORIDIZED PASSIVATION LAYER FOR USE IN PEM FUEL CELLS BIPOLAR PLATES. United States. doi:10.1002/9780470291320.ch28.
Weil, K. Scott, Kim, Jin Yong, Xia, Guanguang, Coleman, J. E., and Yang, Zhenguo. Sat . "DEVELOPMENT OF BORIDIZED PASSIVATION LAYER FOR USE IN PEM FUEL CELLS BIPOLAR PLATES". United States. doi:10.1002/9780470291320.ch28.
@article{osti_948423,
title = {DEVELOPMENT OF BORIDIZED PASSIVATION LAYER FOR USE IN PEM FUEL CELLS BIPOLAR PLATES},
author = {Weil, K. Scott and Kim, Jin Yong and Xia, Guanguang and Coleman, J. E. and Yang, Zhenguo},
abstractNote = {This paper outlines the development of a new low-cost materials concept for polymer electrolyte membrane fuel cells (PEMFCs). Employing the roll bonding process to prepare a nickel clad steel laminate, the thin outer nickel layer is then passivated using a powder pack boridization technique. Results from energy dispersive X-ray (EDX) and X-ray diffraction (XRD) analyses and from scanning electron microscopy (SEM) indicated that a relatively homogeneous Ni3B layer grows on the exposed surfaces of the nickel and that the thickness of this layer can be readily controlled through the time and temperature over which boridization takes place. At high boridization temperatures, ≥ 700ºC, and long periods of time, a Ni2B overlayer forms on top of the Ni3B. Preliminary exposure testing conducted at 80ºC for 300hrs in 1M H2SO4 containing 2ppm HF demonstrates a significant increase in the corrosion resistance that is attributable to the boridization treatment.},
doi = {10.1002/9780470291320.ch28},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sat Feb 04 00:00:00 EST 2006},
month = {Sat Feb 04 00:00:00 EST 2006}
}

Conference:
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  • The bipolar plate is the most bulky component in the PEMFC stack (in both weight and volume) and one of the most expensive to manufacture. It serves not only as the electrical junction between serially connected cells, but also performs several other key functions in the device: • Distribute the fuel and oxidant uniformly over the active areas of the cells. • Facilitate water management of the membrane to keep it humidified, yet mitigate flooding. • Act as an impermeable barrier between the fuel and oxidant streams (particularly H2) to maintain the hydrogen gradient across the membrane necessary for highmore » power output. • Provide some measure of structural support for the stack. • Remove heat from the active areas of the cells. The use of metal-based bipolar plates in PEMFC stacks potentially offers a number advantages particularly for transportation applications including: low-cost, mass-production via stamping or embossing of sheet product; fabrication in very thin form (< 200μm) to reduce weight and volume in the overall stack; impermeability to fuel, oxidant and water vapor; and in general, excellent thermal conduction properties and good mechanical robustness, even as a thin stamped foil. The primary challenge with metal interconnects is surface corrosion, and the current drive to increase the operating temperature of the stack will only exacerbate this problem. Corrosion of the bipolar plate leads to a release of metal ions that can contaminate the electrolyte membrane and poison the electrode catalysts. In addition, the formation of a passivating oxide or oxyhydroxide layer on the surface of the metal will increase the contact resistance between the bipolar plate and the adjacent graphite electrode backing layer by many orders of magnitude. Both conditions can significantly degrade stack performance. A number of researchers have investigated various schemes for protecting metallic bipolar plates, most of which rely on a thin, inert yet electrically conductive coating [1]. The greatest level of success that has been openly reported has been achieved with noble metal coatings such as gold and palladium. Unfortunately commercial use of these materials, even as thin coatings, is cost prohibitive.« less
  • Due to their prospects to attain high power densities and high efficiencies, Proton Exchange Membrane (PEM) fuel cells are among the most promising power sources for a variety of applications. Possible applications include new electric vehicles, on-site power generation in buildings and battery replacements. However, costs and power densities of the fuel cells have to be significantly improved to make the technology competitive. One of the most important components of the PEM fuel cells are the bipolar plates, which separate and distribute fuel and oxidant, provide mechanical support of the membrane electrode assemblies (MEA's), and enable current flow. These platesmore » have to be optimized in terms of cost, size and weight. Requirements of the bipolar plates include mechanical integrity, low electrical resistivity, and stability under fuel cell operating conditions over extended periods of time (10,000+ hours). Work at MER Corporation has been focused on the development of materials and flow designs to reduce cost and weight of bipolar plates. Materials with better mechanical properties than monolithic graphite, low resistivity and good long term stability, which can be formed into net shape or near net shape, have been developed. Different markets and applications demand different operating conditions and consequently different plate and fuel cell designs. Parameters like operating current density, humidification levels, fuel composition, size and weight constrains have been translated to optimum material and design solutions. Three different advanced materials and designs for low cost advanced bipolar plates have been developed and analyzed for cost and performance to realistically assess properties for specific fuel cell target markets. Fuel cells have been assembled and tested using all the developed bipolar plate materials. These results have been compared to the goals set for specific applications in terms of cost and performance.« less
  • A liquid-cooled, bipolar plate separating adjacent cells of a PEM fuel cell comprises corrosion-resistant metal sheets brazed together so as to provide a passage between the sheets through which a dielectric coolant flows. The brazement comprises a metal which is substantially insoluble in the coolant. 6 figs.